The invention relates to a carrier plate for the friction coating, or block, of a brake pad for disc brakes, the carrier plate comprising a disc-shaped molded member of a hard ceramic material whose rear face is provided with a cover.
German Pat. No. 2,734,585 discloses a carrier plate of the above-identified type in which, however, the cover of the rear face consists of a metal sheet. This not only requires an additional molding process for the manufacture of the metal protective cover but also additional measures to connect the molded ceramic member firmly with the protective cover, for example by gluing. Since the friction coating must be pressed onto the frontal face of the molded ceramic member of the carrier plate, there exists the danger that the carrier plate may break during this procedure. The production of molded ceramic members involves firing and/or sintering of the green blank which inevitably leads to certain deviations in dimension or shape due to the so-called shrinkage. Moreover, a slight amount of warping cannot be avoided in practice so that such molded ceramic members "rest hollow" in the pressing mold when the coating material is pressed on and may be destroyed by the compressive pressure even if the rear face is provided with a casing of sheet steel.
The term "hard ceramic material" here refers particularly to hard porcelains and hard ceramics as defined in DIN [German Industrial Standard] No. 40685.211,i.e., a dense hard ceramic material containing predominantly magnesium silicate. In connection with the present invention, however, this term is not limited to the above defined materials but also covers glass and glass ceramics or the like.